Because he is William Gates III, hence the third or Trey(probably called three when he was a kid).
There is no German word "dritt". Maybe someone ment something like "Davis Love III" which is in Germany "Davis Love der Dritte (the third)"
Being short for triple it is sometimes used as a nickname for someone with the suffix "III" i.e. the third name-holder in a family line.
The third generation Golf III and Jetta III produced from 1993 to 1999
The third or, the III
XII-III
You would write their name followed by "III" to indicate they are the third person with the same name in their family. For example, John Smith III.
Last Call - 2011 III is rated/received certificates of: USA:M/PG
The Third Republic
The twenty third sultan of the Ottoman Empire was Ahmed III.
John Doe, III is an example.
If you mean Henry the Third (III) then click on the link below for more information